The R4-B is advertised as a ten tube receiver,but,tube V6 is not used
,there is no V6,,,there are only nine tubes in use. Receiver is
definately a hybrid ..My schematic does not show V6 at all. If you need
a copy I can have one made for you..Double check your schem and see if
V6 is actually there.. 73 W4PQW